1. Field of the Invention
The present invention relates to a method of leaching copper from copper sulfide ore using iodide ion wherein iron (III) ion required is efficiently reproduced using iron oxidizing microbes.
2. Description of the Related Art
In general, as forms of leaching copper from copper sulfide ore by wet smelting process, a form of leaching by a batch stirring reaction using sulfuric acid or hydrochloric acid, a form of leaching by preparing a laminate of the ore, providing sulfuric acid or hydrochloric acid to the top of the laminate and recovering the liquid dropped by gravity (heap leaching method) and the like have been known. Further, a method by utilizing the ability of bacteria such as iron oxidizing microbes for leaching the copper efficiently and recovering it (bioleaching) has been also known.
As the wet smelting process of copper sulfide ore, the bioleaching method and the like have been put to practical use for secondary copper sulfide ore such as chalcocite, covelline and the like. However, there is a problem that as the solubility of primary copper sulfide ore such as chalcopyrite to mineral acids is very low, the leaching rate thereof is very low when the leaching is performed at ordinary room temperature.
With regard to the above-described problem, Japanese Patent Application No. 2009-193197 (Patent Document 1) reports an example that the leaching of copper sulfide ore mainly including chalcopyrite and enargite is promoted at ordinary room temperature in the presence of iodide ion together with iron (III) ion as an oxidizing agent. In the leaching, it is also desirable economically to prepare and provide iron (III) ion used as an oxidizing agent by oxidizing iron (II) ion obtained as the result of the leaching reaction and ferrous sulfate which is inexpensive using iron oxidizing microbes. Further, it is also desirable economically and environmentally that the post-leaching solution is reused as a leaching solution repeatedly without discarding it. However, there have been a problem that as iodine has a powerful germicidal action, it is difficult to reproduce iron (III) ion by using the iron oxidizing microbes in above-mentioned leaching utilizing iodine wherein a solution containing iodine and iodide ion is used.
On the other hand, Japanese Examined Patent Application Publication No. 7-91666 (Patent Document 2) reports an example in which active chlorine is used as an oxidizing agent of iodine and activated carbon and anion exchange resin are used as an adsorbent for removing iodine in the solution. As an exemplary method, there is a method for purifying an aqueous solution of alkali metal chloride in which iodide ion is oxidized to molecular iodine by adding hypochlorous acid or chlorine water and then the solution is passed through the activated carbon where the molecular iodine is adsorbed to the activated carbon, and thus, the iodine in the solution is removed. Further, Japanese Examined Patent Application Publication No. 4-16554 (Patent Document 3) also describes a similar method for removing the iodine in the solution by using an oxidizing agent and activated carbon in the industrial method for electrolytic process of common salt. Further, Japanese Patent Application Publication No. 62-34681 (Patent Document 4) reports, as a method for separating and recovering the iodine from brine, a method in which an ion exchange resin is used. However, the solutions used in these examples of the method for removing the iodine are quite different from the acidic leaching solution from copper sulfide ore containing metal ions such as iron, copper and the like, and therefore it is difficult to apply these methods to the leaching as they are. Further, in these methods, chlorine oxidizing agents having strong toxicity against microorganisms are used. Therefore, even if it is possible to remove iodine from the leaching solution of copper sulfide ore by applying these methods as they are, it is difficult to oxidize efficiently iron by microorganisms in the post-iodine removal solution due to the effect of the remaining chlorine oxidizing agent or chloride ion.
As described above, for leaching copper efficiently from copper sulfide ore mainly including chalcopyrite and enargite, iodide ion and iron (III) ion are required. However, there is a problem that it is difficult to reproduce iron (III) ion and circulate the leaching solution by using iron oxidizing microbes due to the germicidal action of iodine.
Accordingly, an object of the present invention is to provide a method of leaching copper from the copper sulfide ore while iron (III) ion is reproduced efficiently by using microorganisms, on the condition that the method has general-purpose properties at real operation level in the leaching in which iodide ion is used.